Recently, balloon angioplasty procedures have become more prevalent as a way of treating stenosis in arteries in a patient's body. It has also been desirable to provide catheters having as low a profile as possible to reach as far as possible into the most constricted of passages. It is also desirable to continue the flow of blood during inflation of the balloon to prevent ischemia, which may ensue during protracted inflations of the balloon.
The efforts to reduce the profile of catheters has resulted in smaller and smaller lumens within such catheters which are capable of transporting blood through its distal end during balloon inflation. As a result, higher and higher pressures have been needed to push the requisite amount of blood through lumens having reduced cross-sectional areas.
The concept of pumping blood during balloon inflation incorporating a pump was originally described in an earlier U.S. application Ser. No. 100,363, filed Sept. 23, 1987, invented by Bandula Wijay and Paolo Angelini.
In the past, peristaltic pumps have been used to pump blood. These pumps suffer from two disadvantages. First, their ability to develop output pressure is limited, as compared to the pump of the present invention, which is capable of generating pressures to about 300 psig. Secondly, the tube used in peristaltic pumps can suffer from partial disintegration, resulting in a release of particulates into the bloodstream, having undesirable effects.
Not only is it important to pump a specified volume per unit of time through a catheter during coronary angioplasty, but it is also important to be able to get a good idea of the pressures developed by the pump, which can also be used as a means of determining the blood flow rates.
Ordinarily, a positive displacement pump, such as a piston pump, would create pressure pulses with every stroke. The apparatus of the present invention provides a pulsation-dampening mechanism with the pump to smooth out pressure pulses, thereby allowing continuous blood flow as well as precise flow measurements to be possible during balloon inflation. The pump can be built from materials that allow the body, including the pulsation-dampening feature, to be disposable. The pump body can be used in combination with a motor and a drive, with the motor and drive being reusable with each disposable pump body. The pump body of the present invention can also operate in any position and is small enough so that it can be used in emergency situations, such as emergency bypass graft surgery, to keep the patient's heart supplied with blood.
Pulsation dampeners have been in use with generally multi-cylinder piston pumps in the oil and gas business to pump a variety of well fluids as a means of reducing pipe vibration at the pump discharge.
Piston pumps have been employed to pump saline and other medications through intravenous catheters.
Peristaltic pumps have been in use for pumping blood during open-heart surgery to perfuse coronary arteries. Peristaltic pumps are very low-pressure pumps; i.e., 80-120 psig maximum. Peristaltic pumps experience slippage and do not deliver a volumetrically reliable flow. The advent of smaller and smaller angioplasty catheters has made it necessary to develop greater blood pressures to be able to pump a sufficient volume through smaller and smaller catheters during PTCA. The pump of the present invention meets this need.